Computer mice are widely used as computer input devices, but have been implicated in a variety of upper limb disorders including repetitive strain injuries (RSIs), often attributed to mouse designs that require the hand and wrist of a user to be held in a position that is generally towards full pronation, i.e. with the palm facing down and held generally parallel to a work surface on which the mouse is located, and with the fingers and thumb splayed out over the mouse. Attempts have been made to produce alternative designs of mouse.
For example, U.S. Pat. Nos. 6,396,479 and 6,795,058 disclose small body mouse designs intended to be gripped between the tips of the thumb and fingers of the user, but that still require the hand and wrist of the user to be in a generally pronated position.
Another approach uses relatively bulky bodies held in contact with the surface of the palm and extended fingers of a user in a so-called handshake grip. See, e.g. U.S. Pat. Nos. 5,648,798, 5,576,733 and 6,072,471. In general, such devices are manipulated by muscles in the upper limb that are physiologically better suited to gross movements rather than precision form of movements that are often required when manipulating a mouse. Any scope for movement of the devices by flexing of fingers and thumb is of extremely limited extent.
It is also known to use relatively slender, pen-type bodies held in a pencil-type pinch grip, e.g. as disclosed in WO 2005/022374 and US 2003/0160765. The pencil-type pinch grip involves gripping an object between the tips of the index finger and thumb and the side of the middle finger. This grip tends to involve the forearm in more pronation than is ideal and that will increase the use of ulnar and radial deviation movements of the wrist, which are known to be associated with strain of the muscles and tendons of the forearm.
The present invention seeks to provide an alternative approach to computer input device design.